Deny unknown fields for chainspec (#9972)

* Add deny_unknown_fields to chainspec

* Add tests and fix existing one

* Remove serde_ignored dependency for chainspec

* Fix rpc test eth chain spec

* Fix starting_nonce_test spec

json/src/spec/params.rs

@@ -22,6 +22,7 @@ use bytes::Bytes;
 
 /// Spec params.
 #[derive(Debug, PartialEq, Deserialize)]
+#[serde(deny_unknown_fields)]
 #[serde(rename_all = "camelCase")]
 pub struct Params {
 	/// Account start nonce, defaults to 0.